The long range objective of this work is the development of a physicochemical interpretation of early events during the transduction process involving the sense of taste. It is our intention to study the role of diffusional and hydrodynamic factors in determining neural latencies and rise times in test animals, and to investigate the effects of surface active agents on the response to primary tastants. These studies should clarify whether surface activity is a key element in the normal taste response. In addition, we shall study the spectrum of lingual epithelial lipids as a function of pre- and postnatal age in developing sheep. Our aim here is to investigate possible changes in lipid composition with known changes in salt taste specificity that occur with development. This study bears on the validity of a hypothesis suggesting lipids play a key role in salt taste.